Atop A Hawaiian Mountain, A Constant Sniff For Carbon Dioxide

By: Joe Palca
May 13, 2013

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Climate scientists have a good reason to want to get away from it all. To get an accurate picture of the amount of carbon dioxide in the Earth's atmosphere, you have to find places where the numbers won't be distorted by cities or factories or even lots of vegetation that can have a major local impact on CO2 concentrations.

Starting in 1958, scientists from the Scripps Institution for Oceanography have been using an instrument on the top of the Mauna Loa volcano in Hawaii to measure CO2 in the atmosphere. Aiden Colton, an atmospheric scientist with the National Oceanic and Atmospheric Administration, says NOAA now maintains the Scripps Institution's CO2 analyzer, as well as one of its own.

"We sample 24 hours a day on most of our instrumentation," says Colton. "But what we're most interested in is the extremely clean air coming down from the troposphere that's been well-mixed traveling over 2,000 miles in every direction to get here." The troposphere is where the bulk of Earth's atmosphere resides. It's the buildup of carbon dioxide in the troposphere that has climate scientists concerned.

The air Colton analyzes comes from intake ports at the top of the 120-foot tower. Taking air from the top of the tower helps ensure it won't be contaminated with outgassing from the volcano.

Atmospheric carbon dioxide has been rising steadily since measurements began in 1958. But that's not to say there aren't small fluctuations. CO2 concentrations are typically reported in parts per million. Colton says it's not unusual to have a fluctuation of 5 parts per million in any given day.

For that reason, NOAA doesn't put much stock in daily averages. "We're a long-term baseline monitoring station," says Colton. "So we're not interested in what happens hour to hour, day to day, even week to week."

Still, the long-term trends indicate that the amount of carbon dioxide in the atmosphere is continuing to climb, and many scientists are worried about the consequences for the planet's ecological health.

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